DE 10 2004 035 267 B3 reveals a microstructured molded object and a method for its production. The molded object consists of a film, in which at least one hollow structure is introduced. The entire molded object, i.e., both the film and the hollow structures, have a plurality of pores, whose diameter preferably takes on a value between 10 nm and 10 μm. The pores are statistically distributed over the entire molded object. One drawback to this solution is that liquids have to make their way through the molded object across the entire surface, while on the contrary it is advantageous to be able to steer liquids specifically to the cells when culturing biological cells.
DE 10 2009 044 115 A1 shows a microstructured molded object with perforated parts and a method for its production. In this method, a first deformable film with a thickness of less than 1 mm is arranged on top of a second film. The second film has continuous recesses with a diameter of less than 2 mm. The first film is molded into the recesses in the second film, so that cavities arise in the second film. The first film has pores, but the pores are only permeable inside the cavities.
From DE 10 2007 050 976 A1 a method is known for the reshaping of a film in which the film being reshaped is firmly connected to a mold link that has at least one opening. Next, regions of the film being reshaped are subjected to a physical or chemical modification. The so modified film joined to the mold link is inserted into a mold and subjected to a pressure medium which at least partly forms the film into the opening in the mold link.
U.S. Pat. No. 6,599,612 B1 teaches a method for production of a soft, elastic web or film with a continuous pattern of depressions or openings. Such webs are intended as contact surfaces or covering films for absorptive hygiene articles, such as diapers, napkins, wound dressings or the like. In two phases, a microperforation at first and then a macroperforation around four times bigger is introduced into the film by perforated rollers. The resulting microperforations are around 0.05 mm to 0.5 mm in size, while the macroperforations are typically around 0.3 mm to 3 mm in size.
DE 10 2009 044 113 A1 shows a partially perforated microstructured molded object and a method for its production. In this method, a deformable film is partially stretched so that stretch regions of reduced thickness are formed. Next, microstructures are shaped in at least some of the thinned-out stretch regions. Furthermore, pores are created in at least one of the thinned-out stretch regions, while at least some of the undeformed regions remain impermeable.
From EP 0 305 123 A1 a method is known for producing an essentially liquid-impermeable web of material with microbubbles. In this method, a web consisting of a polymer film is transported over a drum. There is a structure on the drum in which the polymer film is shaped by means of a water jet impelled with high pressure, creating microbubbles. In this process, regions remain with practically no thinning out and regions are created with thinning that are shaped deep in the structure. These microbubbles are not pores, simply based on their diameter.
DE 101 34 040 A1 shows a method for production of hollow microfluidic structures made of plastic. In a single process cycle, a thermoplastic synthetic film is thermoshaped into fluidic microstructures by a pressurized gaseous or liquid medium. At the same time, the synthetic film is joined to a rigid or rigid-flexible non-thermoshaped substrate by the action of temperature and pressure.
DE 10 2007 023 286 A1 shows a method for production of a membrane in a frame. In this method, a film is prepared for reshaping and it is reshaped by pressing with a liquid synthetic under pressure into a positive or a negative mold. After the shaping, a solid synthetic is formed, whereupon the composite of unshaped film and solidified melt is removed from the mold.
DE 37 23 404 A1 concerns a liquid-permeable film that is used, for example, as a cover film for absorptive hygiene articles. The film has openings that lie in forms which stick out from the underside of the film. The narrowest point of the forms is recessed relative to the plane of the top side of the film.
In the scientific article by Hebeiss I. et al.: “Novel three-dimensional Boyden chamber system for studying transendothelial transport” in Lab on a Chip, 2012, 12, pages 829-834, the cultivation of cells in microchannel structures is revealed. FIG. 1 of this article shows the production of these microchannel structures, for which a porous film of polycarbonate is formed into a shape. Next, a nonporous film of polycarbonate is placed on the shaped film, while the nonporous film already has recesses so that the shaped regions remain open. A drawback of this solution is that the recesses in the nonporous film have to be positioned with great labor relative to the shaped regions in the porous film so that these match up with each other. This process is not suitable for the mass production of such structures.